Generalized Anxiety Disorder (GAD) is a substantial public health problem (Wittchen et al., 2000). There is growing evidence that the most efficacious treatments for GAD are third-wave behavioral therapies focused on the principles of mindfulness and acceptance (Roemer et al., 2009). At the same time, it seems to be the case that interpersonal variables such as satisfaction with a romantic relationship, partner hostility, and partner accommodation of GAD symptoms negative affect the course and even the response to treatment of GAD (Durham, Allen, & Hackett, 1997; Zinbarg, Lee, & Yoon, 2007). These findings suggest it will be useful to develop a treatment that combines mindfulness of anxiety and worry with an existing couple therapy method that also focuses on increasing mindfulness of interpersonal behavior, Integrative Behavioral Couple Therapy (IBCT). The present study is a treatment development study of such a combined therapy, IBCT-GAD. The primary goal is to establish treatment principles for the conjoint treatment of GAD and conduct a preliminary test of efficacy in altering GAD symptoms, credibility for patients, and proposed mediators (e.g., hostility and relationship satisfaction). In order to make recruitment of an adequate sample of couples who are distressed and also include one partner with GAD more feasible, this test will occur in an online setting. We will build an online version of IBCT-GAD (similar to an existing online IBCT) and recruit forty couples to participate in an open trial.